Eruptions of the Yellowstone volcanic system have included the two largest volcanic eruptions in North America in the past few million years; the third largest was at Long Valley in California and produced the Bishop ash bed.
On the diesel Passat, the TDI badge stands for Turbocharged Direct Injection, which isn't really all that helpful as the gasoline-powered Passat is also turbocharged and also uses direct injection. Volkswagen attempts to clear this up by calling this Passat the Passat TDI Clean Diesel.
Toyota 's (NYSE: TM) Mirai is an electric sedan powered by a hydrogen fuel cell, a device that chemically extracts the energy from hydrogen gas to produce electricity. It's a clean technology -- the only exhaust is water vapor -- but producing hydrogen affordably isn't exactly a clean process right now.